A study published this month in the Open Journal of Pediatrics indicated that just days after the meltdowns in the nuclear reactors at the Fukushima-Dai-ichi plant in Japan in March, 2011, Iodine-131 concentrations in US precipitation was measured up to 211 times above normal, and that the highest levels of I-131 were found in the five US pacific coastal states. The number of congenital hypothyroid cases in these five states from March 17-December 31, 2011 was found to be 16% greater than for the same period in 2010, compared to a 3% decline in 36 other US States. The authors' noted that In the Pacific/West Coast, the largest changes were in the California city of Eureka.

Joseph Mangan and Janette Sherman, the authors of the study, suggest that, "Further analysis, in the US and in other nations, is needed to better understand any association between iodine exposure from Fukushima-Dai-ichi and congenital hypothyroidism risk."